Dispensers that provide for the individual pop-up dispensing of successive wet sheets are known in the prior art. It is believed that the prior art dispensers have been primarily designed to dispense moistened nonwoven webs manufactured by the carding process. As is well known in the art, carded nonwoven webs are made with textile length fibers that are very highly oriented in a machine direction of the web, which, in the finished moistened web product, is perpendicular to the line of perforations which define the interconnecting tabs between individual sheets. Because of the long fibers and their orientation, the dispensing ports for such carded nonwoven webs consist of holes or a slit which exert considerable force on the web as it is being dispensed.
One example of a moistened carded nonwoven web product available in the market place is a lotion impregnated wiper for babies. The carded web, before it is impregnated has a dry basis weight of about 25.4 grams per square meter (15.0 pounds per ream of 2880 square feet) and a thickness after it has been moistened of about 0.22 millimeters (0.0085 inches). The ratio of the thickness (meters) of a wet sheet to the dry basis weight (kilograms per square meter) of the sheet, called the wet bulk ratio, provides a good measure of the bulk of the product. For the previously described baby wiper, the bulk ratio is about 0.00855 meters per kilogram per square meter (0.00057 inches per pound per ream of 2880 square feet).
Carded nonwoven webs and wet wipers made therefrom are generally not perceived by consumers to be bulky. Applicants have found it desirable to make a moistened wiper using relatively bulkier nonwoven webs such as those manufactured by an air-laying process as described in U.S. Pat. No. 3,862,472--Norton et al or by a wet-forming process as described in U.S. Pat. No. 3,879,257--Gentile et al, both patents being assigned to the assignee of this invention. The bulkier nonwoven webs made in accordance with the Norton et al and Gentile et al patents tend to be weaker in the direction perpendicular to the perforations between sheets than comparable carded nonwoven webs because these bulkier webs consist predominately or entirely of short fibers, such as wood pulp fibers and cotton linters, and because the fibers are not as highly oriented in the machine direction when the web is initially formed. Because of this increased bulk and decreased strength in the direction perpendicular to the line of perforations, it has been found that many of the prior art pop-up dispensers are not suitable for dispensing such premoistened webs.
British Pat. No. 7721/1899--Utermohlen discloses a dispenser which utilizes a slot having contacting edges to hermetically seal the contents of the dispenser.
U.S. Pat. No. 2,004,614--Meagher discloses a container having a dispensing opening formed by a plurality of slits which result in flaps that act upon the material being dispensed in such a manner as to sever the material above the dispensing opening rather than in the opening itself.
U.S. Pat. No. 2,806,591--Appleton similarly discloses the use of a dispensing opening for automatically severing the material passing through the opening.
U.S. Pat. No. 4,017,002--Doyle et al, like Utermohlen, disclose forming a dispensing opening with contacting edges for sealing purposes. Doyle et al, like Meagher and Appleton, also disclose using edges of the opening for causing the material to sever. Doyle et al indicate that the container is used as a pop-up dispenser for moist tissues, although Doyle et al do not disclose the critical guidelines with respect to, for example, the type of material being dispensed and how it is perforated. Applicants have found that the dispenser described by Doyle et al cannot satisfactorily dispense bulky, premoistened air-layed and wet formed webs. Because the edges of the slit are so close together, they exert a considerable frictional force on the weaker, bulkier tissue with the result that many sheets tear at places other than the perforations or in some instances where the sheet parts at the perforations, the succeeding sheet does not pop-up through the dispensing slit. Another problem with the Doyle et al dispenser is that as a bulky sheet is dispensed through the slit, it "ropes" excessively, that is it twists and gathers, and the large forces exerted on the sheet by the edges of the slit cause the moisture in the sheet to be extruded off the sheet, particularly where the edges of the slit contact the sheet. This results in the withdrawn sheet having a streaked, uneven distribution of moisture. The Doyle et al patent also discloses a cross-shaped dispensing port formed by two intersecting slits. This dispensing port has the same problems as the single slit dispensing port and additionally, because of the pointed sectors at the center of the dispensing port, has even a greater tendency to tear or shred the bulkier air-layed and wet-formed webs other than at the perforations.
U.S. Pat. No. 3,868,052--Rockefeller discloses a dispensing port for a moist towelette that comprises an aperture and a plurality of sharp projections that extend into the opening of the aperture. As a sheet is dispensed, one or more of the projections catch onto the perforations to start the tearing action. Applicants have found that when dispensing moist, bulky webs, it is undesirable to have sharp projections within the dispensing aperture because the sharp projections tend to catch and tear the web at places other than at the perforations.
U.S. Pat. No. 3,749,296--Harrison discloses a dispensing port in which either a single slit is formed in an inclined plane or two intersecting slits are formed in the surface of an inverted cone. In both embodiments the edges of the slits are in substantially contacting relationship and therefore suffer the disadvantages enumerated in the above discussion of the Doyle et al patent.
U.S. Pat. No. 4,219,129--Sedgwick discloses a dispenser for moist tissues or towelettes in which the dispensing port is a frustoconical orifice. The orifice acts to impose a drag on the roped tissue that is insufficient to cause severance of the end tissue at its line of perforation until this line is advanced by the user beyond the orifice and the exposed tissue is subjected to a snap action, causing severance of the end tissue from the web. The tail of the succeeding tissue now protrudes above the orifice to permit its subsequent extraction.
U.S. Pat. No. 3,973,695 discloses another prior art dispenser for moist tissues in which the dispensing port is an aperture having an enlarged triangular portion at one end and a generally circular portion at the other end. The enlarged triangular portion of the dispensing port facilitates the threading of the lead end of a tissue through the dispensing port. Once the lead end of a tissue is threaded through the dispensing port, the lead end of the tissue is pulled into and through the circular portion of the dispensing port until the lead tissue is completely outside the container. The leading tissue is then pulled radially outward from the container to cause the lead tissue to separate at the perforations.
U.S. Pat. No. 3,982,659--Ross assigned to the assignee of this invention discloses a dispensing port having flexible flaps for dispensing premoistened wipers.
U.S. Pat. No. 2,317,102--McKaig discloses a dispenser for cotton in which a sulphite paper disk has a centrally located circular aperture with cuts or slits extending radially out from the aperture.